Mystery countertop finish

[Packard]

I had a cup of coffee at McDonalds this morning.  While most of the tables had some sort of laminate finish (about 1/8” thick with a printed wood grain, and solid color all the way through), other tables had tops that were difficult to pin down.

Here is an image:

The top is clearly made from some grade of steel, but only mildly magnetic which leads me to believe it is some grade of 400 series stainless steel.

The corners are precisely welded and ground so that there are no seams.

I could feel the thickness of the steel underneath the table and I would guess it was about 0.060” to 0.080”  thick or thicker.

The finish looked like heavily textured powder coating, but was far more abrasion and scratch resistant that powder. 

(I rubbed the edge of a penny against the non-visible edge underneath and none of the finish rubbed off.  So it is not conventional powder.

My best guess is the finish is porcelain. The steel is thicker than would be required to resist dings, and probably was specified to resist warping during the porcelain application. 

Pretty interesting.  This has to be very durable (and ghastly expensive). Why would they specify such an expensive table top?

This company is promoting “tactile porcelain” finish. 
https://www.architecturalmaterials....tactile-metal/tactile-porcelain-enamel-metal/

I could see a hyper-durable finish like this in a hyper-busy location.  But this location is in a strip mall in a small town outside Poughkeepsie.  I doubt that it is a top performing location. 

 

[Lincoln]

Specifications usually apply to all stores, especially in big companies. Over the years we've done a number of stores and had to follow their spec books, with no deviation allowed. From Australia Post through to Subway, they all must stick with the 'bible'.
It's an interesting table top, that's for sure. And, like you say, would be very expensive. Was it on a plywood substrate?

 

[Cheese]

I know that 410 stainless sheet is available but it's tough to find and it is expensive. It's about 2-1/2 times more expensive than 304 sheet. Don't really know what the draw is because 410 is less stain & rust resistant than 304 because of the additional nickel & chrome content in 304. In this application, for a heavily used table top, a 400 series stainless seems like a curious choice unless attaching paper notes with magnets was a priority.  [eek]

 

[Packard]

Specifications usually apply to all stores, especially in big companies. Over the years we've done a number of stores and had to follow their spec books, with no deviation allowed. From Australia Post through to Subway, they all must stick with the 'bible'.
It's an interesting table top, that's for sure. And, like you say, would be very expensive. Was it on a plywood substrate?

I didn’t climb underneath to check, but the outer frame was built up and felt like wood.  I didn’t feel for the field material.  The nex time I’m there, I’ll check.

 

[Packard]

I know that 410 stainless sheet is available but it's tough to find and it is expensive. It's about 2-1/2 times more expensive than 304 sheet. Don't really know what the draw is because 410 is less stain & rust resistant than 304 because of the additional nickel & chrome content in 304. In this application, for a heavily used table top, a 400 series stainless seems like a curious choice unless attaching paper notes with magnets was a priority.  [eek]

The 400 series was a guess, based on the fact that it was only mildly magnetic.  It was apparently a reasonable guess, with the “reasonable-ness being supported here:
https://www.nolifrit.com/news/enamel-coating-on-stainless-steel-67.html

NOTE:  They use “enamel” to mean the process of coating with porcelain.

Ferrite stainless steel [400 series] is magnetic, easy to enamel, with low firing temperature. Austenite stainless steel [300 series]is not magnetic, with very high coefficient of expansion, special enamel frit must be applied to enamel it. And its firing temperature very high. Adherence will be weak with low temperature, as stainless steel inside is not fully oxidized

 

[Packard]

I am having my morning coffee now at McD’s.

The table tops are a full 2” deep.  The major substrate is 3/4” to 1.00” thick sheet goods.  I don’t feel a wood grain, and the outer perimeter seems to be the same stuff.  Textured like Formica, but maybe (probably) expanded foam of some sort.

The mounting plate joining the table top with the base is a full 16” wide.  Why that width?  My guess is that the substrate does not hold screws very well.  If it was plywood, I would expect a smaller mounting plate. 

But why stainless in the first place?  Couldn’t they just have painted the underside and gone with steel.

Note:  Commercial grade carbon steel is C1008 - C1010.  The carbon content makes coating with porcelain problematic. 

When we (the company I used to work for) had to produce parts that got porcelain coated, we had to use C1003 (maximum).  In theory that would not cost extra.  But it is outside the normal production standards, so it is difficult to find in small quantities, and requires a special run of the steel mill. 

So perhaps the C1003 maximum in carbon steel cost nearly as much as the 400 series stainless.  It seems a stretch.  But as difficult as it was for us to obtain C1003 maximum steel, maybe.

Are appliances still being porcelain coated?  The interiors of ovens are.  But elsewhere?

 

[mino]

Interesting.

Indeed looks like some modern ceramic coating, like seen on some cookwae. Never seen "classic" enamel coating that would have this type of a look. Probably covers the part where it is not as hard nor fragile and would explain the need for stainless - traditional enamel is pretty thick and gas-tight, this looks like under 1/16" thick and probably less hard/dense, so may not create a propper anti-rust barrier to use on standard steel.

Also any dent or hairline crack a normal enameled steel would bleed rust while this way it will just stay as a small dent.

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(Classic) enamel coatings are hard/expensive to do and the resulting product is pretty fragile. Over here some cook tops, standalone ovens made in traditional design are still enamel-coated. But not much. The quality and heat resistance of paints went way up ove the last decades, as well as stainless going cheaper comparatively.

Our old washing machine from the early 80s had enamel panels. When replaced after 20 years of service, most of the panels were like new. The replacement one was rusted after 5 years in the same environment .. the last one is good for 10+ by now, after two bearing swaps and still not rusty.
Industrial paints went way up on quality compared to just a couple decades ago.